Overview:

The Hundred Regiments Offensive (August – 5 December 1940) was a major campaign of the Communist Party of China's National Revolutionary Army divisions commanded by Peng Dehuai against the Imperial Japanese Army in Central China. The Japanese North China Area Army estimated the strength of communist regulars to be about 88,000 in December 1939. Two years later, they revised the estimate to 140,000. On the eve of the battle, the Communist forces grew to 400,000 men strong, in 105 regiments. The extraordinary success and expansion of the 8th Route Army against the Japanese had Zhu De and the rest of the military leadership hoping that they could engage the Japanese army and win.
By 1940, growth was so impressive that Zhu De ordered a coordinated offensive by most of the communist regulars (46 regiments from the 115th Division, 47 from the 129th, and 22 from the 120th) against the Japanese-held cities and the railway lines linking them.